The mechanism of "paradoxical" increase of blood diaminoxidase (histaminase) activity under the influence of dimedrol and thiamine

The activity of blood diaminoxidase is changed under the influence of dimedrol and thiamine, i.e., its activity is either inhibited or, on the contrary enhanced. It was established in experiments on pigs and cows that different action of dimedrol and thiamine depends on the initial activity of the enzyme. Thus, when the initial activity of diaminoxidase was high thiamine enhanced its activity, while with low initial activity of the enzyme the latter was inhibited by thiamine. The same principle was also experimentally proved in case of dimedrol. The mechanism of increase of diaminoxidase activity under the influence of dimedrol and thiamine is to a certain extent similar to the phenomenon of the "Haldane paradox".